Hydroxyl terminated reactive liquid polymers can be made in a number of different ways. They can be made from olefinic polymers by initially converting a portion of the olefinic bonds of the polymer to ozonide linkages and then cleaving the ozonide linkages to produce a hydroxyl terminated liquid polymer. Liquid polymers prepared in this fashion do not achieve hydroxyl functionality at each end of the polymer chains and as a result, the final terminal hydroxyl functionality is generally considerably less than 2, on the order of 1.6 to 1.8. For most efficient use of the reactants and best overall properties, it is desirable to have final terminal hydroxyl functionality as close to 2 as possible or greater than 2.
The desired terminal hydroxyl functionality is made more attainable by the use of a process wherein a carboxyl terminated reactive liquid polymer is converted to the corresponding hydroxyl terminated liquid polymer. Terminal functionality of practically 2 can be achieved by this process which is essential if higher polymers are to be produced by the subsequent curing reactions with suitable materials.
The carboxyl terminated liquid polymers for the conversion reaction can be made by the process disclosed in U.S. Pat. No. 3,285,949. Pursuant to this process, a suitable monomer is polymerized in a solvent such as tertiary alkanol and/or acetone in presence of an aliphatic azodicarboxylate initiator such as 4,4'-azobis(4-cyanovaleric acid) radical initiator to form unrefined carboxyl liquid polymer that is washed with water, coagulated, separated by decantation, dried and drummed for storage.
The conversion to the corresponding hydroxyl liquid polymer is made by reacting a carboxyl terminated liquid polymer with a stoichiometric or an excess amount of ethylene oxide, per 100 parts of the carboxyl liquid polymer, in presence of 0.01 to 3 parts of a tertiary amine catalyst. Amount of ethylene oxide is generally 3 to 10 parts per 100 parts of the liquid polymer. The product is then dried by vacuum treatment to remove unreacted catalyst and ethylene oxide and drummed for storage, as disclosed in U.S. Pat. No. 3,712,916.
A process has now been discovered for preparing hydroxyl terminated liquid polymers from corresponding carboxyl terminated liquid polymers that eliminates the steps of coagulating, separating, drying and drumming of carboxyl terminated liquid polymers. Furthermore, impurities originating with ethylene oxide and the amine catalyst can be easily removed by addition of a strong acid and subsequent water washing.